Control and manipulation of magnetic nanoparticles and cold atoms using micro-electromagnets

We have developed micro-electromagnets to control and manipulate both ultra cold neutral atoms in vacuum and magnetic nanoparticles in a fluid. The design and fabrication of these micro-electromagnets are described. We then demonstrate the manipulation of atoms, magnetic nanoparticles, and magnetotactic bacteria using these micro-electromagnets. This thesis consists of two main parts: atom manipulation using planar micro-electromagnet guides, and magnetic particle manipulation using various multi-layer micro-electromagnets.; We have designed, fabricated and experimentally demonstrated a microelectromagnet to guide atoms above a substrate. Micro-electromagnet guides consist of current carrying wires microfabricated on a flat substrate to produce two-dimensional magnetic field minimum that can control the trajectories of cold neutral atoms. Micro-electromagnets can produce magnetic field magnitudes to 0.1 T with field gradients to |∇B| ∼ 104 T/cm because high currents can be applied to microfabricated wires with current densities up to 5 × 107A/cm2. Magnetic field calculations show that the structure of a micro-electromagnet needs to be carefully designed to optimize the loading of atoms into the micro-electromagnet. Experimental results are discussed that demonstrate the guiding of atoms. We discuss the design of new micro- and nano-electromagnets that may be used as beam splitter and interferometer for atoms.; We have also demonstrated the ability of micro-electromagnets to trap, move and assemble magnetic nanoparticles and magnetotactic bacteria in a fluid above a substrate at room temperature. Two types of micro-electromagnets, a ring trap and a matrix, have been fabricated. The ring trap is a single circular Au wire with a smooth insulating layer on top. A ring trap has been demonstrated to trap magnetic particles and magnetotactic bacteria at fixed positions. The matrix consists of two arrays of lithographically patterned Au wires, separated by an insulating layer with a smooth insulating layer on top. By controlling the currents through individual wires, the matrix can produce single or multiple peaks in the magnetic field magnitude that can be continuously moved across the surface to any position, with spatial resolution much less than the wire spacing. Using a matrix, we have trapped and moved magnetic particles and magnetotactic bacteria over the surface. We have also rotated magnetic particles above a fixed position in microscopic region utilizing time-dependent current control. Possibilities to manipulate single nanoparticles using nano-electromagnets are discussed.